Cyber Monday is expected to generate $6.6 billion in internet sales, which would make it the largest U.S. online shopping day in history by $1 billion, according to Adobe Analytics, which measures transactions at the largest 100 U.S. web retailers.

“Consumers have become conditioned to wait for big discounts,” said lead Adobe analyst Tamara Gaffney.

Retail stores have invested heavily in boosting their websites and improving their delivery options in anticipation of shoppers intent on finding the latest round of steals.

“It’s the day when people finish their shopping,” Gaffney said. “That’s why it’s so big. All of those gifts that have built up in the shopping cart, people realize they have to finish otherwise the deals will be gone. It’s a collection bucket for the end of the weekend.”

The annual internet bonanza comes after Black Friday and Thanksgiving online sales surged to record highs.

U.S. retailers raked in a record $7.9 billion in online sales over both days, up 17.9% from a year ago, according to Adobe.

All told, 59% of consumers are expected to shop for deals online this year — the first time online buying will be more popular than shopping in brick-and-mortar stores, according to the National Retail Federation.

“More and more shopping has gone online,” said Dan Eleff, who runs DansDeals, a website that highlights the latest bargains.

Many of the deals will be listed early Monday morning, including some on Amazon expected to be posted at 3 a.m., he said.

“It keeps the excitement up,” he said. “And it also doesn’t tip off competitors and let the other companies undercut them. They make people look on their sites.”

Toys are the best products to buy on Cyber Monday, unless they are high in-demand items, according to analysts. Deal seekers can expect to save up to 17% on toy purchases on Monday, the Adobe review predicts.

That includes deals for Lego sets and “Star Wars” toys, said Lindsay Sakraida, director of content marketing for Dealnews.com.

Many independent brands selling clothing, beauty and travel packages are also offering 30% to 50% off — and sometimes more.

For instance, Gap is offering 50% off coupons, plus another 10% discount, as well as a coupon that waives shipping fees.

“There are pretty strong discounts,” Sakraida said. “Smaller brands are really the ones that shine the most around Cyber Monday.”